The present invention relates to electronic displays and, more particularly, to a method and apparatus for non-scan matrix addressing of a bar display of the liquid crystal type.
There is presently substantial interest in electronic displays of the bar-graph type, i.e., a display in which the length of a column of light is proportional to the magnitude of a parameter being measured. Bar graph displays are known utilizing gas discharge, light emitting diode, liquid crystal and other technologies. Bar displays utilizing liquid crystal technology are particularly advantageous in that a display having a plurality of individual segments, typically greater than 40, can be realized with minimal power consumption for the display element itself. However, both the contrast ratio and the response time of a liquid crystal display utilizing so-called "coincident", or 2D, matrix addressing circuitry is usually a function of the scanning duty cycle. Liquid crystal devices, being RMS responsive, are severely limited by the time sharing requirements of a scanned address matrix, whereby contrast becomes unusably poor and/or response times become unusually long, for duty cycles in excess of about 1 in 32.
Desirably, the response time characteristics of a nonmultiplex system should be retained while facilitating an addressing scheme by which all of the elements of the matrix, regardless of the number thereof, can be driven to full optical saturation.